This invention relates generally to pocket spring assemblies, and in particular to pocket spring assemblies for use in cushions or mattresses. More specifically, the invention relates to apparatus and methods for efficiently producing pocket spring assemblies having a two-dimensional array of pocketed springs.
Most pocket spring assemblies are constructed of two-dimensional arrays of coil springs contained in individual fabric pockets. Such a construction is often referred to as the Marshall construction, being named after its inventor. Although the Marshall construction has provided a desirable level of cushioning performance for almost a century, its usage has been limited for a variety of reasons, primarily being limited by its high cost of manufacture.
For example, one common way of constructing pocket spring assemblies is by producing strings or linear arrays of pocketed springs which are subsequently joined together to form a two-dimensional array of pocketed springs. U.S. Pat. No. 4,234,983 describes one common way of forming strings of pocketed springs which can then be joined together to form a two-dimensional array of pocketed coils. Similar patents describing methods and apparatus for constructing strings of pocketed coils are U.S. Pat. Nos. 4,854,023 and 4,986,518. The complete disclosures of all these patents are herein incorporated by reference.
U.S. Pat. No. 4,578,834 describes techniques for joining strings of pocket springs to form a two-dimensional array of pocketed springs. In this patent, the strings of pocketed springs are connected to each other by an adhesive that is applied between lines of tangency of adjacent coil springs. A hot melt adhesive applicator transverses a string of pocketed coils, depositing a precise amount of adhesive on each coil jacket. A second string is positioned on the first, and pressure is applied thereto. The applicator then traverses the second string in the same manner as the first. The sequence is repeated until a spring assembly of desired size is created. The complete disclosure of this patent is herein incorporated by reference. U.S. Pat. No. 4,234,984 describes another method for joining adjacent strings of pocketed springs by alternately connecting the interior string of springs to the adjacent string on either side.
In summary, common prior art techniques for forming two-dimensional arrays of pocketed springs include the steps of forming strings of pocketed springs and then joining the strings together. Unfortunately, such a process is time consuming and inefficient, thereby increasing the cost of the pocket spring assembly. Hence, it would be desirable to provide a more efficient way to make a two-dimensional array of pocketed springs to thereby reduce the overall cost of the spring assembly. In particular, it would be desirable to provide a way to join strings of pocketed assemblies while the strings are being formed. In this way, a two-dimensional array of pocketed springs may be formed in a single, continuous process.